Sizing fibrous materials



Patented Oct. 18, 1932 UNITED STATES PATENT OFFICE BRUNO WIEGER, OF BRUNSWICK, GERMANIASSIGNOR TO BECKER & CO. (1924:) LIMITED,

' OF "LONDOI. ENGLAND SIZING FIBROUS MATERIALS No Drawing. Application filed August 24, 1929,5ata1 No. 388,275, and in Germany Bay 15, 1929.

The present invention relates to improvements in the sizing of paper, textiles and the like fibrous materials, and concerns more particularly the production of sizing agents to be emp oyed for this purpose.

It is believed that the technical efiectof sizing paper, paper pulp and the like depends upon the reduction of the tendency which the fibres possess forzcapillary absorption, this being achieved by the application to the fibres of substances which are water repelling and insoluble, for example, coloplreny.

In carrying out this operation it has been the practice to mix a soap solution with the paper pulp or the like in the hollander or beater, the soap solution being obtained by treating resin with hot alkali. After thorough admixture of the materials in the heater or hollander, alum (or aluminium sulphate) is added for the purpose of decomposing the soap. The stock so treated may be converted into writing paper, whereas unsized stock produces absorbent papers such as blotting papers and filter papers, and cannot, of course, be used for writing purposes. The sizing effect is much more intensive and etfeetive when the saponification of the resin is achieved with a limited quantity of alkali, so that unsaponified resin is present in the size. The free resin theory is at present largely accepted in technical circles. Thus, for example, to obtain a saponification of colophony corresponding, for example, to a middle saponification number of about 165, roughly 16% of soda calculated as Na COs is required. With 10% of soda, therefore, soluble acid soaps are obtained which contain about 40% of free resin, and these acid soaps containing free resin are widely used at the present time for paper sizing. The reduction of the alkali (soda) below 10% results in the production of an almost or quite insoluble product. The alkali is in quantities such that saponification of the resin for example is negligible.

It has been proposed to disperse resin by means of a colloid mill without the use of alkali, and in fact when such colloidal resin is produced in this way it is found to be very eflicient for the sizing of fibrous materials. Difiiculties arise, however, in the dispersion of resin in colloid mills on account of the small yield produced compared with the excess of power required, and the liability of the mill to become clogged.

Now, according to the present invention, colophony and similar substances which are suitable for sizing, or low melting, insoluble paper sizing agents, such as resins in general, artificial resins, waxes, parafiins, fats, fatty acids. bituminous substances, stable carbohydrates or mixtures of the same with drying oils, their distillation residues and the like, may be made to produce dispersions suitable for use as sizing agents in the following manner:

The materials chosen for sizing are subjected at a temperature in the region of their melting point, and in the presence of an alkaline solution containing one or more of the so-called protective colloids, for example, al bumen, casein and the like, to a short intensive uniform mechanical agitation in a suitable apparatus, for example, in a vessel provided with a stirrer rotating at about 100 to 300 revolutions per minute. The protective colloids in question are those which are efiicacious in extremely small quantities.

The quantity of the protective colloid required is usually small, being for example from 1 to3% of the material to be dispersed. The dis ersions 'thus obtained are readily and uni ormly miscible with cold water.

The dispersions produced in the manner described above depend for their colour upon the material employed, varying from deep yellow to white, and on precipitation coagulate very finely. Moreover, since the sizing media so produced are not soap solutions, only a small quantity of alum is required for precipitation, the effect being not, one of decomposition in the chemicalsense, but the precipitation of a colloid by a salt which, if it is a tribasic salt, is particular y effective in this connection. The use for sizing, of the dispersions produced according to the invention is therefore attended with considerable economy. As the dispersions produced are fluid and in the case of resin may have a content of 50-60% thereof, they do not require dilution before use. Moreover, they have the advantage that they are quite insensitive to hard water and to the process water, which is always acid. Both these factors militate against effective sizing with the older processes.

The method of sizing above outlined shows therefore practical and economical advantages to a high degree, and moreover it is possible according to the invention to employ a considerable number of additional materials for sizing paper and other fibrous products. These materials may be used alone, in admixture or mixture with colophony for sizing fibrous products. Thus, hard resins such as copal, shellac and the like give harder papers with more rattle, while softer papers with a smoother feel may be produced by the addition of fatty substances. In other words, a great number of materials which have a water repelling action may be applied to the sizing of paper.

An additional advantage of the above process resides in the fact that the dispersions may be dyed with basic, water insoluble colouring matters. The colouring matter becomes saline on account of the acidity of the dispersions and then remains fixed to the fibres which thereby become stably coloured.

The following examples will serve to illustrate the manner in which the invention may be carried into effect:

Ewample 1.98 kgs. of melted pine resin is thoroughly agitated in a vessel provided with an eflicient stirring mechanism having strong stirringarms and rotating at about 300 revolutions per minute. During the stirring the material is cooled by the addition of small proportions of water to which, if desired, a small quantity of alkali, for example, 0.13% is added. At a temperature of about 80-90 C. a hot solution of 2% of casein in 25 litres of water and 200 grammes of caustic soda is added, the stirring being continued at the highest available speed. In a few minutes the mixture is converted into an almost colourless mass, which is readily miscible with water. In order to cool the product it is desirable to add cold water to the material during stirring, whereupon the fluid mass takes up the water. The material becomes stiffer at first but soon becomes more fluid. With a resin content of 50% or less, the material remains fluid at ordinary temperature and may be run off into a storage tank. In use it is suitable to employ 2% of the colloidal material (i. e. 1% of resin) in proportion to the stuff content of the hollander or heater. After thorough incorporation of the sizing material with the material to be sized the sizing material may be precipitated, coagulated and fixed with 1% of alum.

Treated in this manner, a paper of middle strength shows a. firstlass sizing efiect.

Example 2.-A quantity of copal, which may be varied as desired, is first melted and then added to resin (colohony), in which it dissolves by reason of the fluid condition of the copal. The mixture is then passed through a metal filter cloth. The melted material so prepared is then dispersed according to Example 1, whereupon the product produced may be employed for sizing. A proportion of 10% of copal in a mixture of copal and colophony gives to the paper a considerably improved hardness and rattle and imparts also a considerably improved finish in machine glazing.

Example 3.-85 kgs. of colophony and 15 kgs. of paraflin are dispersed in the manner described in Example 1. Owing, however, to the reduction in the melting point on account of the presence of the paraflin, the temperature of dispersion may be (SS- U. The prepared product is then used as in Example 1, by adding the same to the heater or hollander. Paper sized with 1% of this mixture shows a considerable improvement in smoothness and softness to the touch.

E .ra-mplc .4.--6O kgs. of copal are melted as in Example 2 and 20 kgs. of shellac and. 20 kgs. of varnish are added to the molten substance. The mixture is then dispersed as described in Example 1, and may then be added to the beater or hollander. Paper sized with this material shows an increased hardness and stiffness as well as a very great elasticity, increased folding-number and good machine glazing effects.

E mample 5.10 kgs. of stearin and 30kgs. of basic colouring matter, or a quantity of the latter necessary to give the desired shade and intensity of colour to the sized material, are added to 60 kgs. of melted resin. The molten mass is dispersed as in Example 1 and employed for sizing by addition to the beater followed by coagulation. If, for example, 1 kg. of the dye stuff is required for 100 kgs. of paper stock, then 6.66 kgs. of a 50% dispersoid of. the material will be required to be added to the beater. The paper so treated will probably be considerably oversized. This may not, however, be undesirable. It is impossible to remove the colouring matter from the material with water.

E wample 6.-A mixture of 60 kgs. of resin, 30 kgs. of copal and 10 kgs. of parafiin are dispersed as in the previous examples. 3% aqueous dispersion is now made which,

with or without the addition of animal and plant sizes, is used in the customary manner for the surface sizing of paper pulp and the like substances. According to t e quantities applied to the material, surfaces ranging from writing up to waterproof or water repelling are obtained. 1

What I claim is 2- 1. The improvement in the production of a resin size, free from any substantial quantity of saponified matter and fromwhich the a small amount of alum, consisting in heating the resin to a temperature in the region of its melting point and subjecting the resin while in the region of its melting point to a short intensive uniform mechanical agitation in the presence of a small amount of a dispersing agent consisting of an aqueous alkaline solution of casein.

2. The improvement in the production of a resin size, free from anysubstantial quantity of saponified matter and from which the resin may be precipitated by the addition of' a small amount of alum, consisting in heatin the resin to a temperature in the region 0% its melting point and subjecting the resin while in the region of its melting pointto a short intensive uniform mechanical agitation in the presence of a small amount of a dispersing agent consisting of an aqueous alkaline solution of a protective colloid.

3. The improvement in the production of a resin size, free from any substantial quans tity of saponified matter and from which'the resin may be precipitated by the addition of a small amount of alum, consisting in heating the resin to a temperature in the region of its melting point and subjecting the resin while in the region of its melting point to a short intensive uniform mechanical agitation inthe presence of a small amount of a dispersing agent consisting of an aqueous alkaline solution of a protective colloid, the amount of protective colloid not exceeding 3% of the resin to be dispersed.

4. The improvement-in the production of a resin size, free from any substantial quantity of saponified matter and from which the resin may be precipitated by the addition of a small amount of alum, consisting in heating the resin to a temperature in the region of its melting point, adding a small amount of alkali to the resin to be dispersed, and thereafter subjecting the resin while in the region of its meltin point to a short intensive uniform mechanica agitation in the presence of a small amount of a dispersing agent consisting of an aqueous alkaline solution of a protective colloid.

5. The improvement in the production of a resin size, free from any substantial quantity of saponified matter and from which the resin may be preci itated by the addition of a small amount 0 alum, consisting in heatin the resin to a temperature in the region 0 its melting point and subjecting the resin while in the region of its melting oint to a short intensive uniform mechanica a 'tation in the presence of a small amount 0 a dispersing agent consisting of an a ueous alkaline solution of a protective colloid, and adding water and permitting the temperature of the mixture to drop while continuing inte'nsive uniform agitation of the mixture.

6. The improvement in the production of a resin size, free from any substantial quantity of saponified matter and from which the resin may be precipitated by the addition of a small amount of alum, consisting in heating'a resinous mixture containing colophony and copal to a temperature in the region of its meltin point and subjecting the mixture while in t e region of its melting point to a short intensive uniform mechanical agitation in the presence of a small amount of a dispersing agent consisting of an aqueous alkaline solution of a protective colloid.

7. The improvement in the production of a resin size, free from any substantial quantity of saponified matter and from which the resin may be precipitated by the addition of a small amount of alum, consisting in heating a resinous mixture containing colophony and wax to a temperature in the region of its melting point and subjecting the mixture while in the region of its melting point to a short intensive uniform mechanical agitation in the presence of a small amount of a dispersin agent consisting of an aqueous alkaline so ution of a protective colloid. 

